One of the perennial challenges for many electronics programs is how to reduce the size and weight of the electronics components. This is important for large systems, such as aircraft and spacecraft, where every savings yields increased payload and mission capabilities. It is equally important for miniature systems, like in vivo medical devices and micro-miniature detectors, where each reduction opens a range of applications previously inaccessible at larger scales.
One of the key constraints on any such system is the demand for some form of local energy to power the electronics. The common solutions include some form of fuel-based power generation (e.g., chemical or nuclear systems), or a storage device (e.g., batteries). Alternative sources, like photovoltaic panels, are also common in specialized applications such as space systems. However, in all of these cases significant amounts of volume and weight are necessarily taken up by the power subsystem components.
While resonant cavities are well known in certain fields, they have not been used to help meet this key challenge. Microwave ovens and lasers are two of the better known examples where resonant cavities are used, but in both these cases the resonant features of the cavity are being used to act as a filter or power amplifier for a locally generated signal. In the case of the microwave ovens, the anode veins serve to define the resonant cavities, which in-turn determine the frequencies that are output when the magnetron is energized. In the typical laser, the laser cavity is formed to allow for optical resonance between a mirrored and a partially mirrored surface. When light is injected into the laser cavity via an exciting element (e.g., a flash tube), the light resonates in the cavity/lasing medium until it has been amplified enough to be emitted as a coherent laser beam. Thus, in both cases, the devices depend on local exciting means. The magnetrons depend upon an interaction of the anode vein-formed cavities with the electrons emitted from the cathode filament and the permanent magnetic field. The lasers depend upon some form of electromagnetic or other pumping means to inject this energy into the lasing medium.
A more recent use of resonant cavities has been to enhance photodetectors. In these devices, the cavity serves to recycle photons at the resonant wavelength, so the quantum efficiency of the photodetectors are dramatically increased. However, these typically rely on a limited range of materials and structures (e.g., vertical photodetector structures, with GaAs or GeSi resonant layers between a reflective layer and the photoabsorption layer), and the photoabsorption layer is the only active layer in the structure. These also remains dependent on local power sources in order to operate.
Thus, in these and other prior art approaches, the use of resonant cavities has been limited to filtering or enhancing locally powered output signals (e.g., magnetrons, lasers), or filtering or enhancing weak signals enough for detection by a locally powered detector. Thus, significant active componentry is still required to drive or extract the desired outputs.
In all these applications, resonant cavities have not been used reduce or eliminate reliance on other local power components. This, together with an advantageous reduction in system size and weight, as well as other challenges addressed in the detailed description below, are solved through our invention.